Endothelial cell seeding of small caliber vascular prostheses in baboons has been shown to promote formation of an endothelial lining and to decrease platelet reactivity after two weeks. Best results were obtained with large innocula of endothelial cells after amplification in cell culture. In the continuation we propose to improve the attachment and growth of endothelial cells on vascular prostheses. The surfaces of the grafts will be coated with fibronectin, different types of collagen, and monoclonal antibodies (to endothelial cells, W6/32) to promote endothelial cell attachment and growth. The effect on endothelial cell attachment and growth will be assessed in vitro. Further evaluation will be done using an in vitro circuit and an ex vivo shunt. The most promising grafts will be studied by carotid implantation in baboons. Enhancement of endothelial cell attachment and growth may result in improved performance of small caliber vascular prostheses. The results of the above studies can be extended to human endothelial cells. The effect on attachment and growth of human endothelial cells on grafts in vitro will be investigated.